Variations in diurnal temperature range over India: Under global warming scenario

Annual, seasonal, and monthly trends in surface air temperature were examined over India during the period 1901-2003. Besides this, annual and seasonal trends were also scrutinized in view of global warming concerns during the 2 non-global (1901-1909 and 1946-1975) and global (1910-1945 and 1976-2003) warming periods as defined by Intergovernmental Panel on Climate Change. A significant increasing trend of 0.743, 0.224, 0.484, and 0.52 degrees C (100 yr)(-1) has been observed in maximum (T-max), minimum (T-min), mean (T-mean) temperatures, and diurnal temperature range (DTR; T-max - T-min), respectively during the period 1901-2003. The annual temperatures (T-mean, T-min, and T-max) show a cooling (warming) tendency during the non-global (global) warming periods, apart from the second non-global warming period of T-max. The seasonal trends in T-min and T-mean also show similar behavior; whereas, T-max shows warming in all sub-periods, excluding the first non-global warming period of the pre-monsoon and monsoon. Seasonal analysis depicts that, both post-monsoon and winter seasons are getting warmer with regard to T-max and T-min. During the analysis as well as in non-global and global warming periods, annual DTR has increased. DTR increases in all seasons, with the largest increase in winter and the smallest in post-monsoon; whereas monthly analysis reveals that all the months, except March, October, and November are contributing significantly to the annual increase of DTR. The partial correlation analysis reveals that the total cloud cover along with the secondary factors like precipitation and soil-moisture are responsible for increase in DTR over India during the period 1948-2003.